1. Field of the Invention
The present invention relates to optical connectors used in optical data transmission and, more specifically, to an optical connector with a shutter in which an inserting port to which a plug of a fiber-optic cable is inserted is opened and closed with the shutter.
2. Description of the Related Art
The optical connecter used in optical data transmission has a basic structure of a combination of a case including an inserting hole to which the plug of the fiber-optic cable is inserted and an optical element arranged at the back part of the inserting hole so as to be optically coupled with the plug inserted into the inserting hole of the case, on both a transmission side and a reception side.
In such an optical connector, closing of an opening, that is, the inserting port of the inserting hole, is carried out with an openable and closable shutter to prevent foreign materials such as dust from entering the inserting hole when the plug of the fiber-optic cable is not inserted.
The shutter generally has a single-swinging hinge structure that pivots with one side rim as the center and, more specifically, includes two types of an outward opening type that opens outward of the case and an inward opening type that open inward of the case. In the case of the outward opening type, an operation of opening the shutter is required when plugging in the plug whereas in the case of the inward opening type, the shutter is automatically opened with the plug-in operation of the plug, and thus the overall evaluation including operationality is higher in the latter inward opening type.
In the case of the optical connecter with the inward opening shutter, a shutter biasing spring is used to elastically hold the shutter in the closed state. For the shutter biasing spring, one type of a torsion coil spring in which a pair of arms projects in two directions from the coil part is mainly used. This is because the hinge shaft of the shutter may be passed through the coil part of the spring or the coil part may be used as the hinge shaft. The optical connecter with the inward opening shutter including the torsion coil spring is disclosed in, for example, U.S. Pat. No. 6,004,043.
In the optical connecter with the inward opening shutter disclosed in U.S. Pat. No. 6,004,043, a single-swinging type inward opening shutter that pivots with the lower rim as the center is used. For the torsion coil spring, the spring including a pair of coil parts on both sides, a U-shaped inner arm projecting from the inner sides of each of the pair of coil parts on both sides and having each distal end coupled to each other, and a pair of outer arms projecting from the outer sides of each of the pair of coil parts on both sides is used.
The coil parts on both sides are externally fitted to the hinge shaft integrally arranged at the back side of the shutter, and the inner arm as well as the outer arms on both sides are widened so that the open angle is greater than or equal to 90° in a state not subjected to external force, and are narrowed so that the open angle is substantially 90° in a state arranged between the back side of the shutter and the inner surface of the lower side of the case, thereby elastically holding the shutter in the closed position.
In such an optical connecter with shutter, with the operation of plugging in the plug of the fiber-optic cable to the plug inserting hole of the case, the shutter moves towards the inside of the case against the biasing force of the biasing spring, and eventually, the shutter moves to a state parallel to the inner surface of the case on the lower side, and the inserting hole completely opens. Here, the inner arm and the outer arms on both sides move towards a direction in which the open angle narrows until they are in a substantially parallel state, and are sandwiched between the shutter and the inner surface of the case on the lower side along with the coil parts on both sides. That is, when the shutter is moved to the opened position, the coil parts on both sides are in a state sandwiched between the shutter and the inner surface of the case on the lower side with the hinge shaft.
Consequently, for the space thickness T for accommodating the shutter in the opened position, the size in which the outer diameter of the coil part is added to the shutter thickness is minimum required (see FIG. 10). The outer diameter of the coil part depends on the thickness of the hinge shaft of the shutter, and a size of a certain extent is required because the hinge shaft cannot be made extremely thin in terms of strength. Thus, the accommodating space of the shutter increases, and further, the entire connecter becomes large.